Use a 25-65 watt iron for most work, and a 150-250 watt one for large cables, or an 8 oz (225 g) gas-heated iron. Working safelyDisconnect both terminals of the battery before doing any work on wiring other than testing. Whenever you work on the car, watch for any part of the loom coming loose from its clips, for there is a risk of it getting trapped or burned. Always replace wiring in its clips.